Field of the Invention
The invention relates to a method for fabricating a semiconductor component having a first oxide layer above a substrate and a capacitor formed above the first oxide layer, in which the capacitor has a metal-oxide-containing capacitor material layer deposited between a bottom electrode and a top electrode.
Conventional microelectronic semiconductor memory components for example, Dynamic Random Access Memories (DRAMs) essentially include a switching transistor and a storage capacitor. In this case, the stored information is represented by the charge state of the storage capacitor. Because of discharge processes, the charge state of a (volatile) DRAM memory cell must be continually renewed.
Oxide or nitride layers having a dielectric constant of at most about 8 are usually used as capacitor dielectrics in DRAMs. In order to reduce the size of the storage capacitor and in order to fabricate non volatile memories, "novel", metal-oxide-containing capacitor materials (paraelectrics or ferroelectrics) with significantly higher dielectric constants are required. Known examples of ferroelectric capacitor materials are SrBi.sub.2 (Ta,Nb).sub.2 O.sub.9 (SBT or SBTN), Pb (Zr,Ti)O.sub.3 (PZT), Bi.sub.4 Ti.sub.3 O.sub.12 (BTO), and a known example of a paraelectric high-epsilon capacitor material is (Ba,Sr)TiO.sub.3 (BST).
The use of these novel capacitor materials poses technological difficulties. First, these novel materials can no longer be combined with polycrystalline silicon, the traditional electrode material. Therefore, it is necessary to use inert electrode materials such as, for example, platinum (Pt) or conductive metal oxides (e.g. RuO.sub.2). The reason for this is that, after deposition, the novel capacitor materials have to be thermally treated ("conditioned"), if appropriate, a number of times in an oxygen-containing atmosphere at temperatures of about 550-800.degree. C., and only the aforementioned inert electrode materials have a sufficient thermostability to avoid an undesirable chemical reaction between the electrode material and the capacitor material.
A further difficulty in the fabrication of such storage capacitors stems from the fact that metal-oxide-containing capacitor materials generally have a high sensitivity to hydrogen. However, after the formation of the storage capacitor, it is necessary to carry out process steps which take place in a hydrogen-containing environment. The disadvantage here is that the Pt electrodes are permeable to hydrogen and do not, therefore, form effective protection against hydrogen damage to the capacitor material.
In principle, there are various possibilities for solving the last-mentioned problem. From the standpoint of materials technology, attempts can be made to find an electrode material which is not permeable to hydrogen, or to find a dielectric material which is not sensitive to hydrogen. In terms of method technology, attempts can be made to avoid, after the formation of the storage capacitor, any process steps which proceed in a hydrogen-containing environment. In all of these solution variants, however, further serious difficulties arise in practice.
In the prior art, attempts have already been made to solve the problem by depositing a hydrogen barrier layer on the storage capacitor. U.S. Pat. No. 5,523,595, which is believed to be the most relevant prior art, describes a method for fabricating a semiconductor component with a ferroelectric storage capacitor. After the construction of the storage capacitor, a hydrogen barrier layer including TiON is produced above the capacitor by a chemical vapor deposition (CVD) process. The barrier layer prevents the penetration of hydrogen through the top Pt electrode of the storage capacitor. The disadvantage, however, is that hydrogen can still penetrate through the bottom Pt electrode and hydrogen can still penetrate laterally into the ferroelectric. Therefore, complete protection of the capacitor ferroelectric against degradation by hydrogen is not given.